You can add the "Third Party Designee" by switching to the Forms mode (Ctrl+2) in TurboTax Desktop version and clicking on "1040 Wks" in the left-hand column and entering the Third Party Designee directly onto the worksheet (see screenshots below)
Note: Double click in the Designee's Name field on the worksheet and the program will allow you to check the "Yes" box.
I’m using turbotax on line on my IPAD to prepare my 97 year old mother’s return. Where/how do I add info for myself as third party designee on her tax return?
Due to the amount of unfortunate fraud that has occurred with cell phone usage in transferring information, TurboTax has worked very hard at protecting your information. Please check your security on your cell phone to make sure that it is acceptable. Should it not be, and if you do not have a home laptop, you can use a library laptop to safely transmit. IPADs carry the same security software so I am just hoping this might be why.